Abstract: Signal processing devices and methods estimate transforms between signals using a least squares technique. From a seed set of transform candidates, a direct least squares method applies a seed transform candidate to a reference signal and then measures correlation between the transformed reference signal and a suspect signal. For each candidate, update coordinates of reference signal features are identified in the suspect signal and provided as input to a least squares method to compute an update to the transform candidate. The method iterates so long as the update of the transform provides a better correlation. At the end of the process, the method identifies a transform or set of top transforms based on a further analysis of correlation, as well as other results.

Abstract: Digital data is optically broadcast through an environment by controllably switching the brightness or chrominance of LED solid state lamps, or of other illumination sources (e.g., television screens and backlit computer displays). This optical data channel is useful to convey cryptographic key data by which devices within the environment can authenticate themselves to a secure network. In some embodiments, the optical modulation is sensed by the camera of a smartphone. The row data output by the smartphone's camera sensor is processed to extract the modulated data signal. In some monochrome embodiments, data communication speeds far in excess of the camera's frame rate (e.g., 30/second), or even the camera's row rate (e.g., 14,400/second) are achieved. Still greater rates can be achieved by conveying different data in different chrominance channels. A great number of other features and arrangements are also detailed.

Abstract: Signal processing devices and methods estimate transforms between signals, and in particular, utilize techniques for estimating phase between a reference signal and a suspect signal. A phase estimation method estimates the phase of reference signal components in a suspect signal using a point spread function. The method provides a set of feature locations representing a discrete reference signal, applies a transform to the reference signal to provide a set of transformed locations, and then uses a point spread function to sample phase from the suspect signal at discrete sample locations in a neighborhood around the transformed locations. This process provides an estimate of phase of the suspect signal at locations corresponding to the transformed locations.

Abstract: A phase deviation method determines translation between a reference and suspect signal by analyzing a phase deviation surface created by computing a deviation metric for phase shift estimates and then analyzing a surface formed from the deviation metrics for an array of translation offsets. The phase deviation method analyzes the deviation surface to determine a translation offset that minimizes phase deviation. This method is applied at increasing levels of detail to refine the translation offset.

Abstract: Signal processing devices and methods estimate transforms between signals, and in particular, utilize techniques for estimating phase between a reference signal and a suspect signal. A phase estimation method estimates the phase of reference signal components in a suspect signal using a point spread function. The method provides a set of feature locations representing a discrete reference signal, applies a transform to the reference signal to provide a set of transformed locations, and then uses a point spread function to sample phase from the suspect signal at discrete sample locations in a neighborhood around the transformed locations. This process provides an estimate of phase of the suspect signal at locations corresponding to the transformed locations.

Abstract: Signal processing devices and methods estimate transforms between signals using a least squares technique. From a seed set of transform candidates, a direct least squares method applies a seed transform candidate to a reference signal and then measures correlation between the transformed reference signal and a suspect signal. For each candidate, update coordinates of reference signal features are identified in the suspect signal and provided as input to a least squares method to compute an update to the transform candidate. The method iterates so long as the update of the transform provides a better correlation. At the end of the process, the method identifies a transform or set of top transforms based on a further analysis of correlation, as well as other results.

Abstract: A phase deviation method determines translation between a reference and suspect signal by analyzing a phase deviation surface created by computing a deviation metric for phase shift estimates and then analyzing a surface formed from the deviation metrics for an array of translation offsets. The phase deviation method analyzes the deviation surface to determine a translation offset that minimizes phase deviation. This method is applied at increasing levels of detail to refine the translation offset.